package bjc.dicelang.v1;

import java.util.Map;

/**
 * A dice expression that refers to a variable bound in a mutable enviroment
 *
 * @author ben
 *
 */
public class ReferenceDiceExpression implements IDiceExpression {
	/*
	 * The enviroment to do variable dereferencing against
	 */
	private Map<String, IDiceExpression> enviroment;

	/*
	 * The name of the bound variable
	 */
	private String name;

	/**
	 * Create a new reference dice expression referring to the given name in
	 * an enviroment
	 *
	 * @param nme
	 *                The name of the bound variable
	 * @param env
	 *                The enviroment to resolve the variable against
	 */
	public ReferenceDiceExpression(String nme, Map<String, IDiceExpression> env) {
		this.name = nme;
		this.enviroment = env;
	}

	/**
	 * Get the name of the referenced variable
	 *
	 * @return the name of the referenced variable
	 */
	public String getName() {
		return name;
	}

	@Override
	public int roll() {
		if(!enviroment.containsKey(name))
			throw new UnsupportedOperationException("Attempted to reference undefined variable " + name);

		return enviroment.get(name).roll();
	}

	@Override
	public String toString() {
		if(enviroment.containsKey(name)) return enviroment.get(name).toString() + "(bound to " + name + ")";

		return name + "(unbound)";
	}
}